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Nonclassical causal modeling was developed in order to explain violations ofBell inequalities while adhering to relativistic causal structure andfaithfulness -- that is, avoiding fine-tuned causal explanations. Recently, ano-go theorem stronger than Bell's theorem has been derived, based onextensions of Wigner's friend thought experiment: the Local Friendliness (LF)no-go theorem. Here we show that the LF no-go theorem poses formidablechallenges for the field of causal modeling, even when nonclassical and/orcyclic causal explanations are considered. We first recast the LF inequalities,one of the key elements of the LF no-go theorem, as special cases of monogamyrelations stemming from a statistical marginal problem; we then further recastLF inequalities as causal compatibility inequalities stemming from anonclassical causal marginal problem, for a causal structure implied bywell-motivated causal-metaphysical assumptions. We find that the LFinequalities emerge from the causal modeling perspective even when allowing thelatent causes of observed events to admit post-quantum descriptions, such asGeneralised Probabilistic Theories (GPT) or even more exotic theories. Wefurther prove that no nonclassical causal model can explain violations of LFinequalities without violating the No Fine-Tuning principle. Finally, we notethat these obstacles cannot be overcome even if one were to appeal to cycliccausal models.

Relating Wigner's Friend scenarios to Nonclassical Causal Compatibility, Monogamy Relations, and Fine Tuning